The Magnetic Tunnel Junction (MTJ) element is positioned at the intersection points of an orthogonal grid pattern formed by the Word and Bit lines in MRAM arrays. Typically, but not necessarily, this cross-point cell architecture (Ref: U.S. Pat. No. 5,640,343, Gallagher et al.) has the bit lines running atop the tunnel junctions and the word lines below, or, in another embodiment, has the word lines running atop the tunnel junctions and the bit lines below.
The bit is switched by the combination of magnetic lines of flux generated by two wires, wherein, at the intersection of which is a uniquely addressable MTJ.
Ferromagnetic Liners (FML) integrated with the wordlines and bitlines enhance MRAM array performance by several means, namely, by allowing lower power consumption for a given switching flux requirement at the tunnel junction, by attenuating nearest neighbor effects and hence aid in tighter packing densities, and by attenuating external stray fields. It is not enough if these word lines and bit lines are clad on two sides. Cladding them on the third side such that the side that is not clad faces the MTJ, enhances the ability of the ferromagnetic liner to steer flux into the MTJ and away from the nearest neighbors. This requires that the bottom lines have a “U” shaped FML, while the top lines require an inverted “U” shaped FML.
We teach herein the art of forming a top strap to the top wordlines so as to achieve an inverted U shaped FML.